Moving object detection and change detection is a well-researched field, with many applications in the security and surveillance domain. Moving object and change detection systems are required to provide automated, robust and real-time detection of moving objects with a high probability of success and a minimal rate of false alarms, without labor-intensive intervention.
Conventional moving object detection and tracking systems are of two generic types; namely, real-time systems and off-line systems. Real-time systems use static low-resolution video cameras, typically HDTV or lower resolution. These video cameras track a pre-designated area, typically limited in size due to the inherent trade-off between field of view and ground sampling distance. Real-time systems generally provide acceptable probabilities of detection, but cover small areas; e.g., an area of 100 m×200 m at 10 cm resolution.
Off-line systems are used to detect changes over longer periods of time and over wider areas than real-time systems. Off-line systems typically operate by comparing satellite or other aerial imagery over time periods ranging from several hours to several months or even years. Off-line systems detect different levels of change than do real-time systems, such as infrastructure changes, which are largely irrelevant to real-time decision making. In addition off-line systems lack robustness with respect to viewing angle, lighting conditions, and other factors.
Robust motion detection generally requires capture of two partially overlapping image frames with substantially similar lighting conditions and perspective. Localization of moving objects in two frames requires the revisit time to be sufficiently short, e.g., less than 0.5 sec, in order to maintain close distances between objects in both image frames. Revisit times that are too short, e.g., less than 0.1 sec, may hide differences between two frames, and prevent calculation of motion parameters. As such, a desirable range for revisit times is 0.1-0.5 sec.
However continuous monitoring of a wide area is practically impossible if a revisit time of 0.1-0.5 sec is to be maintained over the entire area. Typically, revisit times for coverage of a larger area are in the range of 5-120 sec.
There is currently no system that provides real-time moving object detection over wide areas using optical sensors.